Blepharospasm

Involuntary, prolonged contraction of one of the muscles controlling the eyelids, causing them to close. It can be due to photophobia (abnormal sensitivity of the eyes to light), to damage to the cornea (the transparent dome that forms the front part of the eyeball), or to dystonia (abnormal muscle rigidity), for which botulinum toxin (a muscle relaxant) treatment is extremely effective.